// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/win/message_window.h"

#include "base/lazy_instance.h"
#include "base/logging.h"
#include "base/macros.h"
#include "base/win/current_module.h"
#include "base/win/wrapped_window_proc.h"

const wchar_t kMessageWindowClassName[] = L"Chrome_MessageWindow";

namespace base {
namespace win {

    // Used along with LazyInstance to register a window class for message-only
    // windows created by MessageWindow.
    class MessageWindow::WindowClass {
    public:
        WindowClass();
        ~WindowClass();

        ATOM atom() { return atom_; }
        HINSTANCE instance() { return instance_; }

    private:
        ATOM atom_;
        HINSTANCE instance_;

        DISALLOW_COPY_AND_ASSIGN(WindowClass);
    };

    static LazyInstance<MessageWindow::WindowClass> g_window_class = LAZY_INSTANCE_INITIALIZER;

    MessageWindow::WindowClass::WindowClass()
        : atom_(0)
        , instance_(CURRENT_MODULE())
    {
        WNDCLASSEX window_class;
        window_class.cbSize = sizeof(window_class);
        window_class.style = 0;
        window_class.lpfnWndProc = &base::win::WrappedWindowProc<WindowProc>;
        window_class.cbClsExtra = 0;
        window_class.cbWndExtra = 0;
        window_class.hInstance = instance_;
        window_class.hIcon = NULL;
        window_class.hCursor = NULL;
        window_class.hbrBackground = NULL;
        window_class.lpszMenuName = NULL;
        window_class.lpszClassName = kMessageWindowClassName;
        window_class.hIconSm = NULL;
        atom_ = RegisterClassEx(&window_class);
        if (atom_ == 0) {
            PLOG(ERROR)
                << "Failed to register the window class for a message-only window";
        }
    }

    MessageWindow::WindowClass::~WindowClass()
    {
        if (atom_ != 0) {
            BOOL result = UnregisterClass(MAKEINTATOM(atom_), instance_);
            // Hitting this DCHECK usually means that some MessageWindow objects were
            // leaked. For example not calling
            // ui::Clipboard::DestroyClipboardForCurrentThread() results in a leaked
            // MessageWindow.
            DCHECK(result);
        }
    }

    MessageWindow::MessageWindow()
        : window_(NULL)
    {
    }

    MessageWindow::~MessageWindow()
    {
        DCHECK(CalledOnValidThread());

        if (window_ != NULL) {
            BOOL result = DestroyWindow(window_);
            DCHECK(result);
        }
    }

    bool MessageWindow::Create(const MessageCallback& message_callback)
    {
        return DoCreate(message_callback, NULL);
    }

    bool MessageWindow::CreateNamed(const MessageCallback& message_callback,
        const string16& window_name)
    {
        return DoCreate(message_callback, window_name.c_str());
    }

    // static
    HWND MessageWindow::FindWindow(const string16& window_name)
    {
        return FindWindowEx(HWND_MESSAGE, NULL, kMessageWindowClassName,
            window_name.c_str());
    }

    bool MessageWindow::DoCreate(const MessageCallback& message_callback,
        const wchar_t* window_name)
    {
        DCHECK(CalledOnValidThread());
        DCHECK(message_callback_.is_null());
        DCHECK(!window_);

        message_callback_ = message_callback;

        WindowClass& window_class = g_window_class.Get();
        window_ = CreateWindow(MAKEINTATOM(window_class.atom()), window_name, 0, 0, 0,
            0, 0, HWND_MESSAGE, 0, window_class.instance(), this);
        if (!window_) {
            PLOG(ERROR) << "Failed to create a message-only window";
            return false;
        }

        return true;
    }

    // static
    LRESULT CALLBACK MessageWindow::WindowProc(HWND hwnd,
        UINT message,
        WPARAM wparam,
        LPARAM lparam)
    {
        MessageWindow* self = reinterpret_cast<MessageWindow*>(
            GetWindowLongPtr(hwnd, GWLP_USERDATA));

        switch (message) {
        // Set up the self before handling WM_CREATE.
        case WM_CREATE: {
            CREATESTRUCT* cs = reinterpret_cast<CREATESTRUCT*>(lparam);
            self = reinterpret_cast<MessageWindow*>(cs->lpCreateParams);

            // Make |hwnd| available to the message handler. At this point the control
            // hasn't returned from CreateWindow() yet.
            self->window_ = hwnd;

            // Store pointer to the self to the window's user data.
            SetLastError(ERROR_SUCCESS);
            LONG_PTR result = SetWindowLongPtr(
                hwnd, GWLP_USERDATA, reinterpret_cast<LONG_PTR>(self));
            CHECK(result != 0 || GetLastError() == ERROR_SUCCESS);
            break;
        }

        // Clear the pointer to stop calling the self once WM_DESTROY is
        // received.
        case WM_DESTROY: {
            SetLastError(ERROR_SUCCESS);
            LONG_PTR result = SetWindowLongPtr(hwnd, GWLP_USERDATA, NULL);
            CHECK(result != 0 || GetLastError() == ERROR_SUCCESS);
            break;
        }
        }

        // Handle the message.
        if (self) {
            LRESULT message_result;
            if (self->message_callback_.Run(message, wparam, lparam, &message_result))
                return message_result;
        }

        return DefWindowProc(hwnd, message, wparam, lparam);
    }

} // namespace win
} // namespace base
